1. Field of the Invention
This invention relates to material handling boom assemblies and their associated vehicles wherein a material handling member is movable in various paths relative to the supporting vehicle. More particularly, this invention relates to power-driven shovels of a conventional loader type of backhoe mechanism mounted on a tractor or a similar vehicle wherein said mechanism may be greatly simplified.
2. Description of the Prior Art
Tractor mounted backhoe mechanisms are well known in the prior art. Representative of the many patents describing such mechanisms are U.S. Pat. No. 3,412,880 to R. L Tweedale and U.S. Pat. No. 4,074,821 to E. B. Long. Other such patents are common in the literature. Each has essentially the same arrangement comprising a bucket or scoop shovel pivotably supported by a dipper arm or dipper stick assembly which is in turn pivotably supported by a boom which is pivotably attached to a supporting bracket rigidly affixed to one end of a tractor or similar vehicle.
In general, each such arrangement includes a plurality of hydraulic cylinder and piston rod assemblies adapted for controllably driving the several aforementioned elements through their respective pivoting motions. While the exact nature of said motions may differ from one form of backhoe arrangement to another, they each perform substantially the same functions of dipping on appropriately positioned bucket into soil or other material to be excavated, said dipping action being generally in line with the longitudinal axis of the tractor, then actuating the boom and dipper arm so as to draw the bucket toward the tractor until it is full, then generally lifting the filled bucket by pivoting the boom and dipper arm until the filled bucket is above the level of the surrounding ground surface, then pivoting the boom to either side until the filled bucket is no longer over the area being excavated, whereat the bucket is actuated to cause the load to be dumped. Subsequently, the boom is repositioned over the excavation, the boom and dipper arm are appropriately re-extended, the bucket is appropriately positioned for digging, and a further excavating sequence is initiated. This process is repeated as often as may be necessary to accomplish the desired excavating task.
Typically, this type of mechanism is used in forming trenches and other relatively narrow excavations. Extended length excavations are generally formed by periodically repositioning the tractor.
Since conventional backhoe arrangements are commonly affixed to a bracket at one end of the tractor so as to extend outwardly therefrom, the wheels or tracks of the tractor located nearest this end of the vehicle act as a fulcrum about which the opposite end of the tractor may become elevated when the bucket is full and the boom and dipper arm are extended. Therefore, it is a common practice to provide an appropriate counterweight to the opposite end of the vehicle. Additionally, rigid outrigger supports, extending to the sides of the tractor and somewhat forward of the wheel axis, are affixed to the end of the vehicle near the boom supporting bracket.
A second type of material handling apparatus, commonly known as a front end loader or as a skip-loaded or as an UNI-LOADER, a Registered Trademark of J. I. Case Company, comprises a scoop or bucket attached to a vehicle such that it is disposed toward the front of the vehicle. This bucket may be appropriately elevated by boom arms and pivoted about a horizontal axis. The vehicle, with the bucket depressed and positioned to have its concave material holding cavity facing forward relative to the vehicle, may be driven forward into the material to be handled until the bucket is full. The bucket is then rotated about its horizontal axis so that the concave cavity is facing generally upward, and the bucket is then elevated to provide appropriate clearance while the vehicle is repositioned to a location whereat the material is to be off-loaded.
A particular form of such a skip-loader apparatus, specifically identifiable by a Registered Trademark of J. I. Case Company as an UNI-LOADER, provides for the bucket lifting mechanism to be in the form of a pair of booms stradling the body of the tractor from pivot points located near the rear of the tractor, with the distal ends of the booms providing means for attaching the bucket thereto at the front of the tractor. Each boom is caused to pivot in a vertical plane relative to the body of the tractor by a hydraulic cylinder and piston rod assembly, the pair being coupled to act in unison. One end of each cylinder and piston assembly is pivotably attached to the body of the tractor and the other end is pivotably attached to its corresponding boom near the distal end of said boom. The distal ends of each boom, being generally at the front of the tractor, include a depending member, respectively, disposed so as to extend generally downward substantially to the ground surface on which the tractor rests when the booms are in their normal lowered positions. The lower ends of these depending members contain attachment points, on a pivotable plate joining said lower ends, to which the bucket may be rigidly coupled. A second pair of hydraulic cylinder and piston rod assemblies, disposed typically to have one of the pair substantially adjacent, to each of said depending members, are pivotably attached between the distal ends of the booms and corresponding brackets affixed to said pivotable plate. Operation of this second pair of cylinder and piston assemblies, in unison, will cause the pivotable plate to rotate about a substantially horizontal axis, thereby causing rotation of the attached bucket about said horizontal axis. Appropriate additional structural bracing may be incorporated to extend transversely between the booms so as to provide necessary strength to the apparatus.
To further orient the reader as to the details of such examples of the prior art, reference is made to the literature describing the Uni-Loader (A Registered Trademark of J. I. Case Company) Skid Steers, models 1835B and 1845C and the corresponding backhoe attachments for said devices, both manufactured by the J. I. Case Company, of Racine, Wis. As can be observed from said literature, when the backhoe attachment is included, the straddling booms serve no function. Moreover, the stability requirements of such a use of the apparatus necessitates the use of outriggers which precludes any relocation operation of the tractor while the backhoe is in use. Improvement in operational capability, along with a simplification of design, are envisioned by the herein invention.